tests/docker: use --arch-only for installing deps

The Debian QEMU packages require a bunch of cross compilers for
building firmware which aren't available on all host architectures.
Using --arch-only skips this particular requirement and allows us to
install just the dependencies we need.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

tests/docker/dockerfiles/debian-arm64-cross.docker

@@ -13,7 +13,7 @@ RUN apt update && \
         crossbuild-essential-arm64
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a arm64 qemu
+    apt build-dep -yy -a arm64 --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=aarch64-linux-gnu-

tests/docker/dockerfiles/debian-armel-cross.docker

@@ -11,7 +11,7 @@ RUN dpkg --add-architecture armel && \
     apt update && \
     apt install -yy crossbuild-essential-armel && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a armel qemu
+    apt build-dep -yy -a armel --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=arm-linux-gnueabi-

tests/docker/dockerfiles/debian-armhf-cross.docker

@@ -13,7 +13,7 @@ RUN apt update && \
         crossbuild-essential-armhf
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a armhf qemu
+    apt build-dep -yy -a armhf --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=arm-linux-gnueabihf-

tests/docker/dockerfiles/debian-mips-cross.docker

@@ -1,9 +1,9 @@
 #
 # Docker mips cross-compiler target
 #
-# This docker target builds on the debian Stretch base image.
+# This docker target builds on the debian Buster base image.
 #
-FROM qemu:debian9
+FROM qemu:debian10
 
 MAINTAINER Philippe Mathieu-Daudé <f4bug@amsat.org>
 
@@ -16,7 +16,7 @@ RUN apt update && \
 
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a mips qemu
+    apt build-dep -yy -a mips --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=mips-linux-gnu-

tests/docker/dockerfiles/debian-mips64el-cross.docker

@@ -17,7 +17,7 @@ RUN dpkg --add-architecture mips64el && \
 
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a mips64el qemu
+    apt build-dep -yy -a mips64el --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=mips64el-linux-gnuabi64-

tests/docker/dockerfiles/debian-mipsel-cross.docker

@@ -16,7 +16,7 @@ RUN apt update && \
 
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a mipsel qemu
+    apt build-dep -yy -a mipsel --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=mipsel-linux-gnu-

tests/docker/dockerfiles/debian-ppc64el-cross.docker

@@ -12,7 +12,7 @@ RUN dpkg --add-architecture ppc64el && \
 
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a ppc64el qemu
+    apt build-dep -yy -a ppc64el --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=powerpc64le-linux-gnu-

tests/docker/dockerfiles/debian-s390x-cross.docker

@@ -17,7 +17,7 @@ RUN apt update && \
 
 RUN apt update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
-    apt build-dep -yy -a s390x qemu
+    apt build-dep -yy -a s390x --arch-only qemu
 
 # Specify the cross prefix for this image (see tests/docker/common.rc)
 ENV QEMU_CONFIGURE_OPTS --cross-prefix=s390x-linux-gnu-